Police in Mountain View also said they came into contact with Aghdam on Tuesday morning hours before the shooting, after finding her asleep in a parked car. Her family had reported her missing.

Aghdam's brother told CNN affiliate KGTV that after he learned Aghdam was in Mountain View, he feared she would do something dangerous. He declined to be identified by the station.

"I Googled 'Mountain View,' and it was close to YouTube headquarters. And she had a problem with YouTube," he told KGTV, adding that he called police to say "she went all the way from San Diego, so she might do something."

Mountain View police, however, said Aghdam's family members gave no such warning to them, according to the Associated Press.

San Bruno police said Aghdam's motive was still unclear, and there was no evidence to suggest that the three victims she wounded were "specifically targeted," The Los Angeles Times reported.

The shooting quickly exacerbated nationwide tensions over gun violence and proposed gun-control measures, an issue which had already come to a head following a mass shooting at a Florida high school in February.